A refrigeration apparatus is used to cool or maintain the inside of a freezer, for example, to or at a predetermined temperature. The refrigeration apparatus is equipped with a compressor having a variable operating capacity. In the refrigeration apparatus, when a low-operating-capacity operation is performed by lowering the driving frequency for a compressor to reduce the flow rate of refrigerant circulating through a refrigerant circuit, the reduction of the refrigerant flow speed causes reduction of the moving speed of refrigeration oil that is moved by a shear force of the refrigerant flow. Accordingly, a large amount of refrigeration oil is distributed in a tube from an outlet of an evaporator back to the compressor, which is a gas single phase portion in the refrigerant circuit.
If the low-operating-capacity operation continues for a long time, the inside of the compressor becomes deficient in refrigeration oil, resulting in malfunction due to lack of lubrication. Generally, when it is determined that the low-operating-capacity operation has continued for a predetermined time, operational control is performed for forcing the operating capacity of the compressor to increase. Specifically, a high-operating-capacity operation is performed by raising the driving frequency for the compressor to increase the flow rate of refrigerant circulating through the refrigerant circuit. This operational control is called oil recovery mode. The oil recovery mode causes refrigeration oil distributed in the refrigerant circuit to be recovered into the compressor.
In the oil recovery mode, the high-operating-capacity operation is performed regardless of cooling load, which may result in excessively large cooling capacity leading to malfunction such as abnormal increase of the condensing pressure. For example, Japanese Patent Publication No. H06-054186 (Patent Document 1) discloses a refrigeration apparatus that ends the oil recovery mode while monitoring the condensing pressure, in order to avoid such malfunction.